Electronic switching circuits



Jan. 6, 1948. l. E. GRosD'oFF ELECTRONIC SWITCHING CIRCUITS 2 Sheets-Sheet l FiledyDeC. 7, 1943 Bnventor roda Jan. 6, 1948. 1 1. E. GRosDoFF 2,434,153

ELECTRONIC SWITCHING CIRCUITS Filed Dec. 7, 1945 2 Sheets-Sheet 2 4 F/WM 60A/TML 4 P0455 50a/eef 00 TPH 7' '/dit/ Snventor @WE mjf ttorneg Patented Jan. 6, 1948 ELECTRNIC SWITCHING CIRCUITS Igor E. Grosdoff, Princeton, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application December 7, 1943, Serial No. 513,317

(Cl. Z50-27) 6 Claims.

This invention relates to switching circuits such as are suitable for controlling the operation of time measuring apparatus and the like, and has for its principal object the provision of an improved switching circuit and method of operation whereby the controlled apparatus is put into and out of operation in response to signals spaced from one another. A further object is the provision of means for precluding termination of the operation indenitely or for a predetermined period following its initiation.

In accordance with the invention, start and stop signals are applied in co-mmon to the input circuits of start and stop channels, each of which includes an input tube and a multivibrator connected to the output terminals of the input tube. These multivibrators are both so connected to a control tube that this tube functions to initiate the supply of the quantity to be measured in response to the start signal and functions to terminate this supply in response to the stop signal which is spaced from the start signal.

The start and stop channels are so interlocked that the stop channel (l) is blocked until the start signal is transmitted to the control tube and (2) is unblocked by such transmission of the start signal. The channel interlocking means utilized is a duodiode having its anodes connected to a control element of the blocked circuit and one of its cathodes connected to the multivibrator of the start or unblocked channel. The other diode is connected to a delay network which is provided for precluding operation of the stop channel indeiinitely o-r for a predetermined period following the application of the start signal. Suitable means are provided for excluding the effect of this delai7 network so that the supply of the measured quantity may be terminated immediately in response to the application of a stop signal.

The invention will be better understood from the following description considered in connection with the accompanying drawings, and its scope is indicated by the appended claims.

Referring to the drawings:

Figure 1 is a block diagram illustrating the application of the start-stop-stop-delay circuit to a device for measuring small intervals of time in terms of the cycles of a l-kilocycle source, and

Figure 2 is a wiring diagram of the control circuit of the present invention.

While the present invention concerns only the switching circuit of the time measuring device of Figure l, it is helpful to have a general understanding of this device as a whole. It is essentially an electronic stop watch of high precision and is capable of measuring time intervals to one hundred thousandth of a second. Its essential parts and sequency of operation are indicated by the legends and arrow heads of Figure 1. A continuously operating -kilocycle quartz crystal serves as the timing element. The oscillations are passed to a mixer from which they are released by the action of the control circuit of the present invention.

A block of these oscillations representing the time interval measured is passed to the ve stages of electronic counters. Here the oscillations are registered and the number is indicated by means of neon lamps.

Each stage of the counters represents one fractional decimal place of a second. Hence the ca-` pacity of the electron part is 0.99999 of a second in 0.00001 second steps. The whole seconds are counted and indicated on a mechanical counter with four indicating wheels. The total capacity of the counter is 9999.99999 seconds.

In Figure 1, the circuit of Figure 2 is indicated by a box bearing the legend Start-stop-stopdelay.

This circuit includes a terminal 9 and a capacitor I0 through which start and stop signals are applied to the control grids of a pair of input tubes II and I2. The tube constitutes the input of the start channel and the tube I2 the input of the stop channel.

The output circuit of the tube Il is connected to the left hand side of a multivibrator I3. This multivibrator includes two electron discharge elements |4-I5--I6 and I'I-IB-IS, anode resistors 20 and 2 I, and grid resistors 22-23 and 24-25. A neon tube 26 and a resistor 21 are connected in shunt to the resistor 2| for indicating when the multivibrator is in a condition to apply a positive potential to the lower control grid of a control tube 28 which is unblocked by this positive control potential to start the supply of oscillations to the controlled device (in the case of Figure 1, the time measuring device).

At the same time a positive potential is applied to the multivibrator grid I5 and to the cathode 29 of a duodiode 30 through which a grid bias of the stop channel input tube I2 is controlled. The potential of the other cathode 3| is derived either directly or from the controlled device through a, lead 32 and a delay circuit constituted of multivibrators 33, 34 and 35 which are connected in cascade to produce a desired delay, for example a two second delay. Unless both cathodes 29 and 3| are at a positive potential, the ln- 3 put tube I2 is biased off and a stop signal applied to its lower grid is ineffective to terminate the supply of oscillations to the controlled device.

When the cathodes 29 and 3| are both positive, however, a. stop signal applied to the lower grid of the tube I2 operates through this tube and the anode resistor 36 to apply a negative pulse to the grid of the right-hand electron discharge element 4I-42-43 of a multivibrator 40. The multivibrator 40 includes a second electron discharge element 31-38-39 and is provided with a second anode resistor 44, with grid resistors 45-46 and 41-48 and with a neon tube 49 and a resistor 50 connected in shunt to the resistor 44 Vfor indicating when the multivibrator is in a condition to permit the supply of oscillations to the controlled device. It will be noted that the multivibrator control grid 42 and the upper control grid of the control tube 28 have their potential determined by the drop of the resistor 36 so that when the multivibrator element 31-38-39 is conducting, a more negative potential is applied to-these grids.

vThe start and stop channels are provided with test switches 5I and 52.

YA reset switch 53 is open-and-closed for applying a positive potentialto the right hand grids Iand 42 of the multivibrator units I3, 4B and .33 and to the left hand grids of the multivibrator units 34 and 35 preparatory to operation of the circuit. In their reset condition-the right hand sides of the multivibrators I3, 45 Aand 33 and the left hand sides Aof the multivibrators and `35 are conducting as indicated by arrows Aso that a negative potential is applied (il) .to the first or lower control grid of the control tube 28, (2) to the cathode 29 of the diode'35, and-(3) to-the cathode 3l of the diode vunless a switch 54 beclosed for excluding the effect of the delay network and raising the potential `of the cathode .31.,

The switch 54 is closed when immediate cessation of the supply of the measure'dlquantity in response to the rst stop signal -is desired. Switches 54 and 55 are open when-it is desired that the measured quantity be supplied for at least two seconds before it can be interrupted-.by a stop signal. Switch 55 is closed when the measured quantity is to be supplied .for an-indefinite time.

With the switch 54 closed and the various multivibrators in their reset condition, the application of a start signal to the terminale unblocks the tube I I which draws current through the resistor 25 thereby applying a morenegative potential to the grid I8 and transferring current from the right to the left side of the multivibrator I3. This transfer of current results i-n a more positive potential at the lowergrid of the control tube 28, this tube passes current, its cathede ybecomes more positive and-the supply of oscillations to the controlled device is started.

At the Sametime the cathode 29 of the fduodiode 30 is mademore positive, so that, with the .switch 54 closed, the input tube i2 yis unblocked-and responsive to the application of a stop signal.

The application of a stop signal to the tube I2 vrcauses this tube to draw current through the resistor 33 thereby transferring current from the right to the left side of the multivibrator 4.5 and applying a more negative Vpotential to the grid 42 of this multivibratorand to the upper control grid .ofthe control tube 28 which terminates the supplyof oscillations to the controlled device.

With switches 54 and 55 open, a negative pulse .derived from 'the control lpulse source by Way of lead 32 functions to transfer current from the right to the left side of the multivibrator 33 thereby producing a positive pulse which is applied through a capacitor 56 to the grid 57 of the multivibrator 34. As a result, current is transferred to the right side of this multivibrator 34. Hence grid 51 becomes positive and receptive to next negative signal from lead 32. In a similar manner the multivibrator 35 is operated by a positive pulse from the multivibrator 34, and current is transferred to the right side of the multivibrator 35 and the cathode 3| is made more positive. When vthis occurs, the multivibrator functions, as Apreviously explained, to bias oi the control tube 28 rand interrupt the supply of oscillations to the controlled device.

It should be understood that the lead 32 may be connected to any source of pulses to obtain the desired delay. For example, while three multivibrators 33, 34, 35 are used in the circuit of Figure 2, any other number of multivibrators may be included to increase the delay, or the pulse source may be chosen to affect less delay.

While the control circuit has been described as applied to a time measuring device, itis apparent that it is applicable to various types of devices having a mode of operation based on the supply of an accurate block of oscillations or the like cut from the output of a continuously operating source.

I claim as my invention:

l. The combination of a pair of input tubes eachhaving input and output terminals, a control tube having two control grids, a rst multivibrator having a irst electron discharge element connected to one of said output terminals and a second electron discharge element-connected to one of said control grids, a second multivibrator having a rst electron discharge element connected to the other of said output terminals and a second electron discharge element connected to the other of said control grids, means for applying spaced signals to both of said input terminals, and means including a rst diode responsive to the current of the second electron discharge element of saidrst multivibrator for applying a control potential whereby the first of said signals is blocked from the second of said multivibrators and the second of said signals is passed to said second multivibrator, and means including a second .diode connected in parallel with said flrst diode for delayingthe unblocking of said second multivibrator for a predetermined time after current is taken by thesecond electron discharge element vof said rst multivibrator.

2. VThe combination of first and second input tubes provided with output terminals and with parallel-.connected input circuits, means for .blockingrsaidsecond input tube, a control tube having two control grids, a rst multivibrator havinga, iirst yelectron .discharge element connected to the `output terminals of the rst of said input-tubes and a second electron dischargefelement, afsecond multivibrator having `a rst electron discharge element-connected to the output terminals of the second of said input tubes and 4a. second electron discharge element, means for applying spaced signals to said parallel-connected input circuits, means responsive to current produced in the second electron discharge element of said rst multivibrator by the rst of said 'signals .for applying a positive potential to one :of `said control grids 'and to said blocking means, means responsive to current produced in the secnond:electrondischarge element of said second multivibrator by the second of said signals for applying a negative potential to the other of said control grids, and means for precluding the application of said negative potential for a predetermined period following the application of said positive potential. v

3. The combinati-on cf a first inputtube having input and output terminals, a second input tube having input, output and control terminals, a control tube having first and second control grids, a rst multivibrator having a first electron discharge element connected to the output terminal of said first input tube and a second electron discharge element connected to the f rst grid of said control tube, a second multivibrator having a rst electron discharge element connected to the output terminal of said second input tube and a second electron discharge element connected to the second grid of said control tube, means for applying spaced signals to both of said input terminals, a iirst diode connected between the second electron discharge element of said first multivibrator and the control terminal of said second input tube, a second diode connected in parallel with said first diode, and means including a third multivibrator connected to the cathode of said second diode for delaying operation of said second multivibrator for a predetermined time interval after current is taken by the second electron discharge element of said rst multivibrator.

4. The combination of a first input tube having input and output terminals, a second input tube having input, output and control terminals, a control tube having rst and second control grids, a first multivibrator having a first electron discharge element connected to the output terminal of said rst input tube and a second electron discharge element connected to the iirst grid of said control tube, a second multivibrator having a first electron discharge element connected to the output terminal of said second input tube and a second electron discharge element connected to the second grid of said control tube, means for applying spaced signals to both of said input terminals, a first diode connected between the second electron discharge element of said first multivibrator and the control terminal of said second input tube, a second diode connected in parallel with said first diode, means including a third multivibrator connected to the cathode of said second diode for delaying operation of said second multivibrator for a predetermined time interval after current is taken by the second electron discharge element of said first multivibrator, and

means for selectively changing the length of said of said control tube, a second multivibrator having a rst electron discharge element connected to the output terminal of said second input tube and a second electron discharge element connected to the second grid of said control tube, means for applying spaced signals to both of said input terminals, a iirst diode connected between the second electron discharge element oi said iirst multivibrator and the control terminal of said second input tube, a second diode connected in parallel with said rst diode, means for applying a control potential, and means responsive to said control potential for applying to the cathode of said second vdiode a potential for delaying operation of said second multivibrator for a predetermined time interval after current is taken by the second electron discharge element of said rst multivibrator.

6. The combination of a rst input tube having input and output terminals, a second input tube having input, output and control terminals, a control tube having first and second control grids, a iirst multivibrator having a rst electron discharge element connected to the output terminal of said rst input tube and a second electron discharge element connected to the rst grid of Said control tube, a second multivibrator having a first electron discharge element connected to the output terminal of said second input tube and a second electron discharge element connected to the second grid of said control tube, means for applying spaced signals to both of said input terminals, a rst diode connected between the second electron discharge element of said first multivibrator and the control terminal of said second input tube, a second diode connected in parallel with said first diode, means for applying a control potential, means responsive to said control potential for applm'ng to the cathode of said second diode a potential for delaying operation of said second multivibrator for a predetermined time interval after current is taken by the second electron discharge element of said iirst multivibrator, and means for changing the extent of said delay.

IGOR E. GROSDOFF.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,272,070 Reeves Feb. 3, 1942 2,324,314 Michel July 13, 1943 2,348,016 Michel May 2, 1944 2,332,300 Cook Oct. 19, 1943 2,240,289 Dillenberger et al. Apr. 29, 1941 1,987,440 Habann Jan. 8, 1935 2,363,810 Schrader et al Nov. 28, 1944 FOREIGN PATENTS Number Country Date 355,705 Great Britain Aug. 24, 1931 

